Sara Amorim

Impact of Traffic Overload on Road Pavement Performance

Traffic on a road pavement is characterized by a large number of different vehicle types, and these can be considered in pavement design by using truck factors to transform the damage they apply to the pavement to the damage that would be applied by a standard axle. The truck factors to convert trucks into standard axles or the load equivalent factors to convert axles into standard axles are defined by considering the average loads for each axle. This process includes the vehicles that travel with axle loads above the maximum legal limit. There are also a substantial number of overloaded vehicles in terms of total vehicle weight. These axles/vehicles cause significant damage to the pavements, increasing the pavement construction and rehabilitation cost. Thus, this paper investigates the impact of overloaded vehicles on road pavements by studying the truck factors for different vehicle cases applied to a set of pavements composed of five different asphalt layer thicknesses and five different subgrade stiffness moduli. The study revealed that the presence of overloaded vehicles can increase pavement costs by more than 100% compared to the cost of the same vehicles with legal loads.

Interactions between exogenous FGF-2 and sulfonic groups: in situ characterization and impact on the morphology of human adipose-derived stem cells.

FGF-2 is often used as a supplement to stem cells culture medium aiming at preserving their self-renewal capacity and plasticity through the passages. However, little is known on the influence of the underlying substrate in these interactions. In this study, we have used mixed self-assembled monolayers with different ratios of -SO3H and -OH tail groups to investigate the influence of substrate properties (e.g., charge) on the FGF-2 adsorption and activity. QCM-D data demonstrated that, in the presence of -OH groups, the quantity of the adsorbed FGF-2 is proportional to the percentage of surface -SO3H groups. The bioactivity of the adsorbed FGF-2 follows the same tendency as demonstrated by its interactions with anti-FGF-2. Surprisingly, the adlayer of FGF-2 formed on the surface containing only SO3H-tailed SAMs was similar to the surface with 25% of -SO3H groups, demonstrating that FGF-2 adsorption is not solely driven by electrostatic interactions. We related these results with changes in the morphology of adipose-derived stem cells (ASCs) cultured on the same surfaces.

Bacteria-responsive multilayer coatings comprising polycationic nanospheres for bacteria biofilm prevention on urinary catheters

UNLABELLED This work reports on the development of infection-preventive coatings on silicone urinary catheters that contain in their structure and release on demand antibacterial polycationic nanospheres. Polycationic aminocellulose conjugate was first sonochemically processed into nanospheres to improve its antibacterial potential compared to the bulk conjugate in solution (ACSol). Afterward the processed aminocellulose nanospheres (ACNSs) were combined with the hyaluronic acid (HA) polyanion to build a layer-by-layer construct on silicone surfaces. Although the coating deposition was more effective when HA was coupled with ACSol than with ACNSs, the ACNSs-based coatings were thicker and displayed smoother surfaces due to the embedment of intact nanospheres. The antibacterial effect of ACNSs multilayers was 40% higher compared to ACSol coatings. This fact was further translated into more effective prevention of Pseudomonas aeruginosa biofilm formation. The coatings were stable in the absence of bacteria, whereas their disassembling occurred gradually during incubation with P. aeruginosa, and thus eradicate the biofilm upon release of antibacterial agents. Only 5 bilayers of HA/ACNSs were sufficient to prevent the biofilm formation, in contrast to the 10 bilayers of ACSol required to achieve the same effect. The antibiofilm efficiency of (HA/ACNSs)10 multilayer construct built on a Foley catheter was additionally validated under dynamic conditions using a model of the catheterized bladder in which the biofilm was grown during seven days. STATEMENT OF SIGNIFICANCE Antibacterial layer-by-layer coatings were fabricated on silicone that efficiently prevents Pseudomonas aeruginosa biofilm formation during time beyond the useful lifetime of the currently employed urinary catheters in medical practice. The coatings are composed of intact, highly antibacterial polycationic nanospheres processed from aminated cellulose and bacteria-degrading glycosaminoglycan hyaluronic acid. The importance of incorporating nanoscale structures within bacteria-responsive surface coatings to impart durable antibacterial and self-defensive properties to the medical indwelling devices is highlighted.

A model for equivalent axle load factors

Most design methods for road pavements require the design traffic, based on the transformation of the traffic spectrum, to be calculated into a number of equivalent passages of a standard axle using the equivalent axle load factors (EALFs). In general, these factors only consider the type of axle (i.e. single, tandem or tridem), but they do not consider the type of wheel on the axles, i.e. single or dual wheel. The type of wheel has an important influence on the calculation of the design traffic. The existing design methods assume that the EALFs are valid for all pavement structures and do not consider the thickness and stiffness of the pavement layers. This paper presents the results of the development of a model for the calculation of the EALFs considering the type of axle, the type of wheel and the constitution of the pavement. The model was developed based on the tensile strain at the bottom of the asphalt layer that is responsible for bottom-up cracking in asphalt pavement, which is the most widely considered distress mode for flexible road pavements. The work developed in this study also presents the influence of the type of wheel (single and dual) on pavement performance. The results of this work allowed the conclusion that the EALFs for single wheels are approximately 10 times greater than those for a dual wheel. This work also proposes average values for the EALFs. An artificial neural network was developed to calculate the EALFs.

Nanocomposites of poly(ε-caprolactone) doped with titanium species

Organic–inorganic hybrid nanocomposites were prepared via in situ sol–gel process. The organic phase is a biodegradable polymer, poly(ε-caprolactone) (PCL), while the tetrabutyl titanate (TBT, Ti(OBu)4) was used as inorganic precursor. Synthesis parameters like acidity medium and precursor amount were investigated in order to assess their influence on hybrid properties. The obtained nanocomposites were characterised by thermal analysis, spectroscopic techniques, transmission electronic microscopy (TEM) and X-ray diffraction to gather information on the structure of the nanocomposites. Mechanical properties and biodegradability were also evaluated. A reaction mechanism based on Fourier transform infrared spectroscopy and NMR results was proposed using methyl acetate as model compound. TEM micrographs of the nanocomposites show a fine good nanoparticles dispersion. Acidic conditions and 10 wt% of precursor lead to a nanocomposite with higher mechanical properties and biodegradability than PCL.

Surfaces Mimicking Glycosaminoglycans Trigger Different Response of Stem Cells via Distinct Fibronectin Adsorption and Reorganization

We report on the utility of a platform created by self-assembled monolayers to investigate the influence of the degree of sulfation of glycosaminoglycans (GAGs) on their interactions with fibronectin (Fn) and the impact of these interactions on the adhesion and morphology of human adipose derived stem cells (ASCs). We used the label-free QCM-D, AFM and SPR to follow the changes in the protein adlayer in close proximity to the substrates surface and QCM-D in combination with live imaging to characterize the adherent cells. Our results suggest that Fn interactions with GAGs are governed by both H-bonding and electrostatic forces. Strong electrostatic interactions cause irreversible change in the protein conformation, while the weaker H-bonding only partially restricts the protein flexibility, allowing Fn reorganization and exposure of its binding sites for ASC adhesion. These findings imply that a delicate balance between these two types of forces must be considered in the design of biomaterials that mimic GAGs.

Molecular weight of surface immobilized hyaluronic acid influences CD44-mediated binding of gastric cancer cells

The physiological importance of the interactions between hyaluronic acid (HA) and its main membrane receptor, CD44, in pathological processes, e.g. cancer, is well recognized. However, these interactions are mainly studied in solution, whereas HA in the extracellular matrix (ECM) is partially immobilized via its interactions with other ECM components. We therefore, developed substrates in which HA is presented in an ECM-relevant manner. We immobilized HA with different molecular weights (Mw) in a Layer-by-Layer (LbL) fashion and studied the interactions of the substrates with CD44 and two human gastric cancer cell lines that overexpress this receptor, namely AGS and MKN45. We demonstrate that MKN45 cells are more sensitive to the LbL substrates as compared with AGS. This difference is due to different CD44 expression: while CD44 is detected mainly in the cytoplasm of AGS, MKN45 express CD44 predominantly at the cell membrane where it is involved in the recognition and binding of HA. The invasiveness of the studied cell lines was also evaluated as a function of HA Mw. Invasive profile characterized by low cell adhesion, high cell motility, high expression of cortactin, formation of invadopodia and cell clusters was observed for MKN45 cells when they are in contact with substrates presenting HA of high Mw.

The functionalization of natural polymer-coated gold nanoparticles to carry bFGF to promote tissue regeneration

Gold nanoparticles (AuNPs) enable the treatment and real-time monitoring of several diseases, providing an exciting and advantageous nanomedicine strategy. These NPs have therefore been adequately functionalized to enable them to carry growth factors (GF), namely basic fibroblastic (bF) GF, which play an essential role in different and important cellular processes including cellular proliferation, survival, migration and differentiation. The AuNPs were coated with natural polymers, chitosan and heparin, to enhance their physicochemical properties such as suspension stability. The polyelectrolyte coating was monitored using a quartz crystal microbalance with dissipation, size and zeta-potential analysis. The natural polymer-coated AuNPs have a spherical shape and a positive surface charge due to chitosan amino groups, enabling their biofunctionalization with monoclonal antibodies to target specific biomolecules. Additionally, cellular assays with the chondrocyte cell line ATDC5 show that the NPs are cytocompatible at relevant concentrations. As a proof of concept of their potential application in tissue regeneration, the natural polymer-coated AuNPs were further functionalized with an antibody to selectively bind the desired GF. The bFGF concentration reached in the NPs without compromising the cytocompatibility demonstrates the potential of this carrier for tissue regeneration.

Fish sarcoplasmic proteins as a high value marine material for wound dressing applications

Fish sarcoplasmic proteins (FSP) constitute around 25-30% of the total fish muscle protein. As the FSP are water soluble, FSP were isolated from fresh cod (Gadus morhua) by centrifugation. By SDS-PAGE, it was possible to determine the composition of FSP extracts (FSP-E). The FSP-E undergo denaturation at 44.12 ± 2.34° C, as characterized by differential scanning calorimetry thermograms (DSC). The secondary structure of FSP-E is mainly composed by α-helix structure, as determined by circular dichroism. The cytocompatibility of FSP-E, at concentrations ranging from 5 to 20 mg/mL, was investigated. Concentrations lower than 10 mg/mL have no cytotoxicity cultures of fibroblasts over 72 h. Further on, FSP membranes (FSP-M) were produced by spin coating to evaluate its properties. FSP-M shown having uniform surface as analyzed by Scanning Electron Microscopy (SEM). The relative amount of α-helix structures is higher when compared with the FSP-E. The FSP-M have higher temperature stability than the FSP-E, since they presented a denaturation temperature of 58.88 ± 3.36° C, according to the DSC analysis. FSP-M shown distinctive mechanical properties, with a stiffness of 16.57 ± 3.95 MPa and a yield strength of 23.85 ± 5.97 MPa. Human lung fibroblasts cell lines (MRC-5) were cultured in direct contact with FSP-M, demonstrating its cytocompatibility for 48 h. Based on these results, FSP can be considered a potential biomaterial recovered from nature, for wound dressing applications.